Cards are a common organizing unit for modern user interfaces (UI). At their core, they’re just rectangular containers with borders and padding. However, when utilized properly to group related information, they help users better digest, engage, and navigate through content. This is why most successful dashboard/UI frameworks make cards a core feature of their component library. This article provides an overview of the API that bslib provides to create Bootstrap cards.
Setup code
To demonstrate that bslib cards work outside of Shiny (i.e., in R Markdown, static HTML, etc), we’ll make repeated use of statically rendered htmlwidgets like plotly and leaflet. Here’s some code to create those widgets:
library(bslib)
library(shiny)
library(htmltools)
library(plotly)
library(leaflet)
plotly_widget <- plot_ly(x = diamonds$cut) %>%
config(displayModeBar = FALSE) %>%
layout(margin = list(t = 0, b = 0, l = 0, r = 0))
leaflet_widget <- leafletOptions(attributionControl = FALSE) %>%
leaflet(options = .) %>%
addTiles()Shiny usage
Cards work equally well in Shiny. In the
examples below, replace plotly_widget with
plotlyOutput() and leaflet_widget with
leafletOutput() to adapt them for Shiny server-rendered
plots/maps.
Hello card()
A card() is designed to handle any number of “known”
card items (e.g., card_header(), card_body(),
etc) as unnamed arguments (i.e., children). As we’ll see shortly,
card() also has some useful named arguments (e.g.,
full_screen, height, etc).
At their core, card() and card items are just an HTML
div() with a special Bootstrap class, so you can use
Bootstrap’s utility classes to customize things like colors,
text, borders,
etc.
card(
card_header(
class = "bg-dark",
"A header"
),
card_body(
markdown("Some text with a [link](https://github.com)")
)
)Some text with a link
Implicit card_body()
If you find yourself using card_body() without changing
any of its defaults, consider dropping it altogether since any direct
children of card() that aren’t “known” card()
items, are wrapped together into an implicit card_body()
call.1
For example, the code to the right generates HTML that is identical to
the previous example:
card(
card_header(
class = "bg-dark",
"A header"
),
markdown("Some text with a [link](https://github.com).")
)Some text with a link.
Restricting growth
By default, a card()’s size grows to accommodate the
size of its contents. Thus, if a card_body() contains a
large amount of text, tables, etc., you may want to specify a
height or max_height. That said, when laying
out multiple cards, it’s likely best not
to specify height on the card(), and instead, let the
layout determine the height layout_column_wrap().
Although scrolling is convenient for reducing the amount of space
required to park lots of content, it can also be a nuisance to the user.
To help reduce the need for scrolling, consider pairing scrolling with
full_screen = TRUE (which adds an icon to expand the card’s
size to the browser window). Notice how, when the card is expanded to
full-screen, max_height/height won’t effect
the full-screen size of the card.
card(
max_height = 250,
full_screen = TRUE,
card_header(
"A long, scrolling, description"
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Elit eleifend iaculis praesent – eu ante enim magna. Dui fringilla neque nibh; enim pellentesque mus torquent venenatis montes? Condimentum duis ornare egestas vehicula fames, tempor imperdiet urna turpis! Quisque etiam ut massa vestibulum, litora magna odio, morbi magna hac tempor. Sapien penatibus scelerisque auctor congue – ullamcorper vehicula quis suspendisse nulla.
Adipiscing luctus orci volutpat fusce, class pulvinar fermentum, est est? Sociosqu etiam sed ridiculus senectus donec, fusce laoreet, augue massa arcu. Erat ac vivamus posuere diam felis quam primis, eleifend dis facilisi. Parturient montes scelerisque auctor purus mi. Est augue nullam ligula sed a sodales purus molestie!
Lorem quisque convallis purus, velit gravida tincidunt quisque nisl eros vulputate accumsan sodales at. Arcu rhoncus congue inceptos ligula sociosqu euismod vehicula nisl taciti blandit eleifend. Potenti hac ac laoreet rutrum malesuada. Integer suspendisse molestie, conubia inceptos! Fames lacus auctor ante, praesent sed bibendum facilisis taciti commodo lobortis.
Filling outputs
A card()’s default behavior is optimized for
facilitating filling layouts. More
specifically, if a fill item (e.g.,
plotly_widget), appears as a direct child of a
card_body(), it resizes to fit the card()s
specified height. This means, by specifying height = 250
we’ve effectively shrunk the plot’s height from its default of 400 down
to about 200 pixels. And, when expanded to full_screen, the
plot grows to match the card()’s new size.
card(
height = 250,
full_screen = TRUE,
card_header("A filling plot"),
card_body(plotly_widget)
)Most htmlwidgets (e.g., plotly, leaflet, etc) and some other Shiny
output bindings (e.g, plotOutput(),
imageOutput(), etc) are fill items by
default, so this behavior “just works” in those scenarios. And, in some
of these situations, it’s helpful to remove card_body()’s
padding, which can be done via spacing
& alignment utility classes.
card(
height = 275,
full_screen = TRUE,
card_header("A filling map"),
card_body(
class = "p-0",
leaflet_widget
),
card_footer(
class = "fs-6",
"Copyright 2023 RStudio, PBC"
)
)Fill item(s) aren’t limited in how much they grow
and shrink, which can be problematic when a card becomes very small. To
work around this, consider adding a min_height on the
card_body() container. For example, try using the handle on
the lower-right portion of this card example to make the card
taller/smaller.
This interactive example is a bit contrived in that we’re using CSS
resize to demonstrate how to make plots that don’t shrink beyond a
certain point, but this concept becomes quite useful when implementing
page-level filling layouts (i.e.,
page_fillable()) with multiple
cards.
card(
height = 300,
style = "resize:vertical;",
card_header("Plots that grow but don't shrink"),
card_body(
min_height = 250,
plotly_widget,
plotly_widget
)
)Troubleshooting fill
As you’ll learn more about in filling
layouts, a fill item loses its ability to fill when
wrapped in additional UI element that isn’t a fillable
container. To fix the situation, use as_fill_carrier() to
allow the additional element to carry the potential to fill from the
card_body() down to the fill item.
Multiple card_body()
A card() can have multiple card_body()s,
which is especially useful for:
- Combining both resizable and non-resizable contents (i.e., fill items and non-fill).
- Allowing each
card_body()to have their own styling (via inline styles and/or utility classes) and resizing limits (e.g.,min_height).
For example, when pairing filling output with scrolling content, you
may want min_height on the filling output since the
scrolling content will force it to shrink:
card(
height = 375,
full_screen = TRUE,
card_header(
"Filling plot, scrolling description"
),
card_body(
min_height = 200,
plotly_widget
),
card_body(
class = "lead container",
lorem::ipsum(paragraphs = 10, sentences = 5)
)
)Elit curabitur nostra turpis habitant facilisi sed, morbi eu penatibus aptent. Eros sodales rhoncus sociosqu, porta augue praesent litora sagittis ut malesuada fames. Dictum ante mi dictum cubilia mollis mi donec iaculis pretium. Rutrum aliquam sed quis tempus lacus, ut mollis vestibulum tincidunt. Na tincidunt.
Sit laoreet metus nunc fermentum laoreet elementum massa fusce lacus? Turpis diam per hac sollicitudin mollis magna faucibus nibh porta. Dui sem hendrerit placerat vestibulum iaculis eget egestas quam non. Duis accumsan diam diam risus mus torquent suspendisse vestibulum vel nascetur. Na nascetur.
Ipsum rhoncus lacinia aliquam feugiat ornare posuere nisi semper venenatis volutpat? Egestas magnis mus turpis; interdum pharetra netus hendrerit penatibus aptent sociis. Sociosqu velit aliquam vulputate tempus purus sodales. Primis fringilla platea massa vel fermentum posuere pulvinar nulla lobortis nunc porta viverra lacus. Purus hendrerit at posuere semper euismod aptent facilisi aptent integer vel leo laoreet!
Ipsum urna suscipit donec posuere duis: massa parturient interdum. Luctus torquent nostra scelerisque condimentum – aptent sed bibendum proin. Orci mattis consequat fringilla gravida mollis habitant, faucibus iaculis congue varius! Parturient condimentum augue posuere tempus vulputate maecenas porta mus, parturient justo ut. Mus donec aenean pretium, libero hac quis faucibus nisl.
Ipsum donec purus ante imperdiet sollicitudin donec parturient lacinia. Fringilla conubia hac gravida porttitor curae senectus vulputate ut? Torquent donec aliquam urna at. Mauris tellus mollis curae pharetra suspendisse metus tempor curabitur a integer. Volutpat lacinia torquent proin curae quisque lectus morbi – cubilia nascetur praesent risus dui, sociis viverra vivamus pellentesque?
Consectetur class, nascetur sociis, pulvinar netus tristique facilisi! Eu varius arcu arcu est; magnis suspendisse convallis tristique netus est. Dis vehicula potenti phasellus, suspendisse donec lectus tellus commodo sollicitudin. Hac ac suscipit neque sapien blandit sapien auctor etiam, id id. Condimentum nunc netus molestie morbi.
Consectetur ante sociosqu bibendum massa urna nunc eu fringilla penatibus! Blandit suspendisse platea mauris conubia etiam, fringilla suspendisse, aliquet: lobortis odio risus vel? Eleifend ultricies odio metus himenaeos sapien torquent dis, tempus tempor mauris accumsan. Blandit penatibus commodo cursus sem purus senectus primis. Fringilla luctus rutrum diam pharetra suscipit nulla nascetur cum, habitasse suscipit himenaeos justo!
Consectetur sem aenean vulputate viverra, felis vestibulum facilisis augue vehicula? Ut fusce natoque purus cubilia cubilia nullam, commodo senectus montes augue. Metus vulputate senectus mus porttitor non venenatis turpis! Nisi auctor euismod suscipit pretium pretium ad magnis fringilla dignissim. Tempor vehicula non neque.
Ipsum per convallis pulvinar, dis varius nullam bibendum hac non nam. Praesent imperdiet ultrices nibh aliquet: ut id scelerisque! Euismod hac sociosqu blandit blandit at quis in ante suscipit lacus primis. Cum senectus bibendum: nullam nunc duis nullam nec senectus quam nec. Na nec.
Lorem facilisis gravida dapibus montes eu non netus cubilia. Venenatis lectus fames aliquam massa, cum imperdiet sed. Curae sagittis quis enim nisi porta dui vulputate ridiculus lacus cum duis? Habitasse quisque elementum, euismod ultrices, integer mauris nulla sociis id per donec. Nibh egestas vehicula vehicula venenatis dictumst quis leo tristique nascetur!
Also, when the content has a fixed size, and should not be allowed to
scroll, set fill = FALSE:
card(
height = 350,
full_screen = TRUE,
card_header(
"Filling plot, short description"
),
plotly_widget,
card_body(
fill = FALSE, gap = 0,
card_title("A subtitle"),
p(class = "text-muted", "And a caption")
)
)A subtitle
And a caption
Multiple columns
As you’ll learn in column-based
layouts, layout_column_wrap() is great for multi-column
layouts that are responsive and accommodate for filling output. Here we have an equal-width
2-column layout using width = 1/2, but it’s also possible
to have varying column
widths.
card(
height = 350,
full_screen = TRUE,
card_header("A multi-column filling layout"),
card_body(
min_height = 200,
layout_column_wrap(
width = 1/2,
plotOutput("p1"),
plotOutput("p2")
)
),
lorem::ipsum(paragraphs = 3, sentences = 5)
)Lorem lacus tempor senectus et pellentesque pharetra interdum fringilla; integer dignissim? Penatibus volutpat bibendum porttitor at quis ridiculus aliquet! Euismod nisi – ligula sem bibendum ac montes himenaeos phasellus. Netus cras convallis ad vulputate, curabitur integer venenatis pretium enim ad primis suspendisse. In gravida nullam velit bibendum mollis, imperdiet mi etiam praesent iaculis tempor rutrum.
Dolor ac sagittis mus placerat fermentum ullamcorper fusce conubia ad. Neque lectus at quis praesent non. Mus arcu id sollicitudin ut, condimentum, parturient sagittis etiam placerat fames venenatis? Consequat ultricies cursus bibendum neque aliquet lacinia justo libero. Et curabitur dui orci ac eget aliquet at, lectus sodales semper convallis nam nunc malesuada orci sociosqu.
Elit condimentum eleifend molestie facilisi, condimentum ut tempus! Dictum curabitur eleifend mattis luctus varius: venenatis ut magna eleifend commodo. Urna facilisi eros phasellus bibendum, cras litora lobortis ac. Tincidunt vehicula euismod volutpat lacus erat nibh semper: orci massa semper rhoncus leo morbi. Viverra lobortis luctus, torquent, porta penatibus aenean euismod torquent aliquam.
Multiple cards
layout_column_wrap() is especially nice for laying out
multiple cards since each card in a particular row will have the same
height (by default). Learn more in column-based layouts.
layout_column_wrap(
width = 1/2,
height = 300,
card(full_screen = TRUE, card_header("A filling plot"), plotly_widget),
card(full_screen = TRUE, card_header("A filling map"), card_body(class = "p-0", leaflet_widget))
)Multiple tabs
navset_card_tab() and navset_card_pill()
make it possible to create cards with multiple tabs or pills. These
functions have the same full_screen capabilities as normal
card()s as well some other options like title
(since there is no natural place for a card_header() to be
used). Note that, each nav_panel() object is similar to a
card(). That is, if the direct children aren’t already card
items (e.g., card_title()), they get implicitly wrapped in a
card_body().
library(leaflet)
navset_card_tab(
height = 450,
full_screen = TRUE,
title = "HTML Widgets",
nav_panel(
"Plotly",
card_title("A plotly plot"),
plotly_widget
),
nav_panel(
"Leaflet",
card_title("A leaflet plot"),
leaflet_widget
),
nav_panel(
shiny::icon("circle-info"),
markdown("Learn more about [htmlwidgets](http://www.htmlwidgets.org/)")
)
)Sidebars
As you’ll learn more about in sidebar
layouts, layout_sidebar() just works when placed inside
in a card(). In this case, if you want fill
items (e.g., plotly_widget) to still fill the card
like we’ve seen before, you’ll need to
set fillable = TRUE in layout_sidebar().
card(
height = 300,
full_screen = TRUE,
card_header("A sidebar layout inside a card"),
layout_sidebar(
fillable = TRUE,
sidebar = sidebar(
actionButton("btn", "A button")
),
plotly_widget
)
)Static images
card_image() makes it easy to embed static (i.e.,
pre-generated) images into a card. Provide a URL to href to
make it clickable. In the case of multiple card_image()s,
consider laying them out in multiple cards
with layout_column_wrap() to produce a grid of clickable
thumbnails.
card(
height = 300,
full_screen = TRUE,
card_image(
file = "shiny-hex.svg",
href = "https://github.com/rstudio/shiny"
),
card_body(
fill = FALSE,
card_title("Shiny for R"),
p(
class = "fw-light text-muted",
"Brought to you by RStudio."
)
)
)Flexbox
Both card() and card_body() default to
fillable = TRUE (that is, they are CSS flexbox
containers), which works wonders for facilitating filling outputs, but it also leads to
surprising behavior with inline tags (e.g., actionButton(),
span(), strings, etc). Specifically, each inline tag is
placed on a new line, but in a “normal” layout flow
(fillable = FALSE), inline tags render inline.
card(
card_body(
fillable = TRUE,
"Here's some", tags$i("inline"), "text",
actionButton("btn1", "A button")
),
card_body(
fillable = FALSE,
"Here's some", tags$i("inline"), "text",
actionButton("btn2", "A button")
)
)That said, sometimes working in a flexbox layout is quite useful,
even when working with inline tags. Here we leverage flexbox’s gap
property to control the spacing between a plot, a (full-width) button,
and paragraph. Note that, by using markdown() for the
paragraph, it wraps the results in a <p> tag, which
means the contents of the paragraph are not longer subject to
flexbox layout. If we wanted, we could do something similar to render
the actionButton() inline by wrapping it in a
div().
card(
height = 325, full_screen = TRUE,
card_header("A plot with an action links"),
card_body(
class = "gap-2 container",
plotly_widget,
actionButton(
"go_btn", "Action button",
class = "btn-primary rounded-0"
),
markdown("Here's a _simple_ [hyperlink](https://www.google.com/).")
)
)In addition to gap, flexbox has really nice ways of handling otherwise difficult spacing and alignment issues. And, thanks to Bootstrap’s flex utility classes, we can easily opt-in and customize defaults.
card(
height = 300, full_screen = TRUE,
card_header(
class = "d-flex justify-content-between",
"Centered plot",
checkboxInput("check", " Check me", TRUE)
),
card_body(
class = "align-items-center",
plotOutput("id", width = "75%")
)
)Shiny
Since this article is statically rendered, the examples here use
statically rendered content/widgets, but the same card()
functionality works for dynamically rendered content via Shiny (e.g.,
plotOutput(), plotlyOutput(), etc).
An additional benefit that comes with using shiny is the ability to
use getCurrentOutputInfo() to render new/different content
when the output container becomes large enough, which is particularly
useful with card(full_screen = T, ...). For example, you
may want additional captions/labels when a plot is large, additional
controls on a table, etc (see the value
boxes article for a clever use of this).
# UI logic
ui <- page_fluid(
card(
max_height = 200,
full_screen = TRUE,
card_header("A dynamically rendered plot"),
plotOutput("plot_id")
)
)
# Server logic
server <- function(input, output, session) {
output$plot_id <- renderPlot({
info <- getCurrentOutputInfo()
if (info$height() > 600) {
# code for "large" plot
} else {
# code for "small" plot
}
})
}
shinyApp(ui, server)Appendix
The following CSS is used to give plotOutput() a
background color; it’s necessary here because this documentation page is
not actually hooked up to a Shiny app, so we can’t show a real plot.